In a device for setting operating parameters of an internal combustion engine, programs of differing priority in time are executed. High-priority programs are all those which must ensure that, at a specific crank angle, a specific operation is triggered, for example ignition takes place or the injection of fuel is started or this operation is terminated. These programs therefore as a rule synchronize operations with the crankshaft rotation. These programs, which are very short and which are started in dependence on the crankshaft, taken as a whole are referred to in the following as synchroprogram. In contrast to the synchroprogram in terms of priority are programs which, for example, evaluate characteristic fields or characteristic lines in order to prepare initial values for programs of higher priority. Such low-priority programs taken as a whole are referred to in the following as a background program. Between the background program and the synchroprogram in terms of priority there is a group of time-dependent programs which serve mainly for any integration purposes. It is important for these programs that they are called up at time intervals adhered to as closely as possible, and during each execution a value, for example the integral value of the regulating quantity for adjusting the lambda value, is increased or decreased by a predetermined count value. Since the count value is fixed, a desired integration speed can be achieved only when the time interval between two integration steps is as constant as possible.
The execution of the background program HGP from its start HGPA to its end HGPE and of the group of time-dependent programs GZAP according to the state of the art is shown in FIG. 1. The group of time-dependent programs GZAP and parts of the background program HGP are run through alternately. During the execution of the background program, a check is made as to whether a timer has set a flag which indicates that a predetermined grid interval ZSR has expired since the last start of the group of time-dependent programs. This grid interval amounts, for example, to 10 ms. In contrast, the pure running time of the group of time-dependent programs amounts, for example, to only approximately 4 ms and that of the synchroprogram to less than 1 ms. However, the run-through of the background program or of the group of time-dependent programs is interrupted repeatedly by the highest-priority synchroprogram. The result is that the actual running time of the group of time-dependent programs at a high engine speed is no longer 4 ms, but, for example 8 ms. Approximately 2 ms then remain within the grid interval for running through parts of the background program.
Methods and devices for setting operating parameters of an internal combustion engine have long been provided in the form of various extension stages. In very simple systems, only a few influencing variables are taken into account and only a few operating parameters are calculated, while in complex systems considerably more calculations take place and also learning operations of the most diverse kinds are carried out. As a consequence, the group of time-dependent programs GZAP is composed of differing numbers of time-dependent programs ZAP, for instance of four time-dependent programs ZAP1-ZAP4 in the example according to FIG. 2. The more programs are accommodated within the group of time-dependent programs GZAP, the more time is taken to run through this group. The state of the art took this into account by increasing the grid interval ZSR. If the pure running time of the group amounted, for example, to 6 ms instead of the above-mentioned 4 ms, resulting at a high engine speed in a genuine running time of 12 ms instead of 8 ms, the grid interval ZSR was fixed, for example, at 14 ms. Such a lengthening of the grid interval was possible and is still possible without difficulty, since the mentioned times are sufficiently short by far to make it possible to run through time-dependent operations with sufficient accuracy. However, changing the grid interval gives rise to the disadvantage that it is necessary to match operating parameters to the changed grid interval, for example the counting steps in integration operations. The practical use of the method and device in an internal combustion engine, namely the so-called application, therefore is relatively complex.
It is the object of the invention to provide an easily applicable device and an easily applicable method for setting operating parameters of an internal combustion engine.